University Appointment

Research & Clinical Interests

Photobiological regulation of the circadian and neuroendocrine systems

Jefferson's Light Research Program was founded in 1984. We study human neuroendocrine, circadian, and neurobehavioral responses to light using techniques of photobiology, radioimmunoassay, radioenzyme assay, as well as standardized psychophysical and psychiatric tests. Our development of an analytical action spectrum for the regulation of pineal melatonin by light wavelength, led in part, to the recent discovery of a novel class of photoreceptors in the eye that are responsible for the neurobehavioral effects of light in humans. The action spectrum showed that the human circadian system is most strongly regulated by blue wavelengths. Currently, our research is both basic and applied. Our basic studies on healthy humans are intended to elucidate the fundamental elements for circadian phototransduction in the eye. Our applied studies translate that basic science into both nonclinical and clinical applications. A significant concentration of our research is supported by the National Space Biomedical Research Institute, a division of NASA. Many astronauts experience sleep and circadian disruption during space flight that can lead to serious decrements in alertness and performance. This risk factor can threaten the safety of individual astronauts as well as entire missions. Our laboratory is testing nonpharmacological lighting countermeasures for these problems. If successful, these lighting countermeasures will be employed in orbiting spacecraft as well as habitats being developed for the Lunar and Mars missions. Shiftworkers here on earth also experience sleep and circadian problems and may ultimately benefit from the lighting countermeasures being developed for space exploration. In terms of clinical applications, we are studying how to improve light therapy for patients with Seasonal Affective Disorder (SAD) or winter depression. We are also testing whether or not light exposure during the nighttime is a risk factor for the development of breast and other types of cancers.